Energy source device



APril 1962 J. SILVERMAN 3,031,519

ENERGY SOURCE DEVICE Filed Aug. 7, 1956 INVENTOR Jose 0h Sill/firm: BYMK RNEY United States Patent 3,031,519 ENERGY SOURCE DEVICE JosephSilverman, Hicksville, N.Y., assignor to Associated Nucleonics, Inc., acorporation of New York Filed Aug. 7, 1956, Ser. No. 602,578 15 Claims.(Cl. 136-89) The present invention relates to nuclear energy, and, moreparticularly, to a unitary device for supplying such energy andconverting the same to light and electrical energy.

Accordingly, an object of the present invention is to provide such adevice, with or without cell means in assembly therewith, which is smallin size, compact in arrangement, light in weight and economical tomanufacture.

Another object is to provide such a device which is capable of producingan electrical output on an order to perform useful work.

A further object is a long useful life.

Other and further objects of the invention will be obvious upon anunderstanding of the illustrative embodiment about to be described, orwill be indicated in the appended claims, and various advantages notreferred to herein will occur to one skilled in the art upon employmentof the invention in practice.

In accordance with the present invention, the foregoing objects areaccomplished by providing an energy source device for converting thedisintegrating energy of a radioactive or nuclear source to light andthen electrical energy which comprises a sealed receptacle, a source ofprincipally beta radiation emissive particles essentially free fromgamma radiation and a phosphor confined and arranged in the receptacleso that light emitted by the phosphor in response to disintegration ofthe source can be directed on photovoltaic cell means adapted to convertthe light to electrical energy.

A preferred embodiment of the invention has been chosen for purposes ofillustration and description, and is shown in the accompanying drawing,forming a part of the specification, wherein:

FIG. 1 is a plan view of a invention including a source means.

FIG. 2 is a sectional view taken along the line 2-2 on FIG. 1.

FIG. 3 is a schematic Wiring diagram illustrating the connection of thecell means in an electrical energy supply circuit.

Referring to the drawing in detail a device is shown, FIGS. 1 and 2,which essentially comprises a receptacle 10, a radioactive source 11 anda phosphor 12 confined in the receptacle. Photovoltaic cell means 13adjacent the phosphor are adapted to be energized by the light emittedby the phosphor in response to disintegration of the source to producean electrical output.

The source and phosphor may comprise an admixture of radioactive sourceand phosphor powders, a source in solution or colloidal suspension in aliquid phosphor, or a layer containing or consisting of a radioactivesource adjacent one or more layers of a phosphor.

The receptacle is illustrated as being shallow or disclike. Theperipheral geometrical configuration of the receptacle may be varied tosuit the purpose for which the device is employed and is shown herein asbeing semicircular for insertion into a circular case containing amechanism to be powered by the battery.

The receptacle 10 may be formed of transparent materials such aspolystyrene or polymerized methyl methacrylate through which lightradiations ranging from the visible to the ultra-violet in the spectrumare adapted to be transmitted. A strip 14 of aluminum foil or itsequivato provide such a device which has device in accordance with thedevice and photovoltaic cell lent is applied to the peripheral wallportion of the receptacle, for example, at the interior of thereceptacle, and a sheet 15 of aluminum foil or its equivalent is appliedto each of the end wall portions of the receptacle. The sheets 15 haveone or more openings 16 therein, two being shown in each sheet by Way ofexample, which provide windows, and a photovoltaic cell 13 is positionedin each of the openings. The aluminum foil or its equivalent serves as alight reflecting means adapted to direct the light emitted by thephosphor through the windows and onto the light sensitive means of thecells to more efiicia ently utilize the emitted light for conversion toelectrical energy. The aluminum foil strip 14 is impervious to betaparticles, whereby radiation damage to the peripheral wall portion ofthe receptacle is prevented.

The foregoing arrangement renders the receptacle opaque and confines theemitted light therein except as the light passes into the cells 13.Alternatively, the cells 13 and the sheets 15 could be positioned withinthe receptacle adjacent the end walls, or the cells could be sopositioned and sheets 15 with or without openings 16 could be applied tothe exterior of the end walls to render the receptacle opaque. Also, itwill be appreciated that the receptacle and cells may be of suchdimensions whereby a cell at each side would constitute the end wall andwould render the receptacle opaque thereat without resorting to sheets15. Still another arrangement which is contemplated comprises moldingthe cells into the end wall structure to unitize the receptacle and cellassembly. In certain cases for example where the reflectors 15 are atthe interior or are omitted, the receptacle may be formed of materialwhich renders it opaque. In all cases, it is desirable that thereceptacle is sealed securely to confine the source and phosphortherein.

As previously indicated, the radioactive source and phosphor may be inlayer or sandwich arrangement. In the preferred form of the device alayer of source material 11 is sandwiched between a pair of layers ofphosphor material 12. The -layers of phosphor material are impervious tobeta ray penetration, whereby radiation damage to the portions of thereceptacle adjacent such layers is prevented.

However, in a simplified but less efficient device having a window orwindows at only one side wall portion, it is conceivable that a layer ofsource material could be placed adjacent a dense or opaque windowlesswall portion and a layer of phosphor material could be placed betweenthe source layer and the windowed wall.

In the foregoing preferred arrangement, the source layer 11 may beapowder, a metal foil or a powder dispersed in a foil, and the phosphorlayer 12 may be a single crystal, a packed powder or a liquid.

In a practical embodiment of the device illustrated herein, thereceptacle is formed of optical grade polystyrene having a thickness ofabout .007 inch. The receptacle has a thickness of about .0515 inch, andis semicircular in-form, with the straight peripheral edge portionhaving a length of about .675 inch, whereby the volumetric capacity ofthe receptacle is about .0067 cubic inch. The layer 11 has a thicknessof about .0115 inch, and the layers 12 have a thickness of about .013inch. The aluminum strip 14 has a thickness of about .008 inch, thereflector sheets 15 have a thickness of about .005 inch, and the cells13 have a thickness of about .010 inch, whereby the overall thickness ofthe device does not exceed about .0715 inch.

The thickness of the phosphor layers 12 is sufficient to stop betaparticles emitted by the radioactive source, whereby all significantradiation is confined to the sandwich or is stopped by the aluminum foilstrip 14, whereby a highly efficient conversion of beta rays tolight isattained.

A suitable source of radioactive material is Pm O and a suitablephosphor is hexagonal zinc sulphide (ZnS) preferably activated with .0l%copper powder. A more efificient light emitting unit can be provided bythese materials by employing a source layer 11 comprising an admixtureof 48 mg. of the activated zinc sulphide and 5.7 mg. of the carrier-freePm O and a phosphor lager 12 consisting of 54 mg. of the activated zincsulp 'de.

This intermediate source layer 111 is relatively thin (.0115 inch) andthe source particles are well scattered therein because of the 5.7 to 48ratio of Pm O to zinc sulphide. Since hexagonal zinc sulphide has arelatively low light absorbing coefficient, the layers 12 and the layer11 are suificiently translucent to enable light reflected by the sheet15 at one end wall to be directed through these layers and impinge onthe cell means 13 or the sheet 15 at the other end wall. If suchreflected light is of a high value, it is conceivable that it may beagain reflected in the opposite direction through the layers to impingeon the cell means at the end walls where reflection first took place, adinfinitum.

The use of a mixture of source and phosphor powders in the layer '11also reduces self-absorption of the radioactive emissions to a minimum.Thus, absorption taking place results in a more efiicient production oflight.

The source is equivalent to 4.5 curies of Pm which has a 2.7 yearsone-half life and has a beta power output of 2200 microwatts, falling edto 1000 microwatts at the end of three years. This source is a pure betaemitter with a maximum beta energy of .22 m.e.v. The beta to lightconversion causes about 550 microwatts to be emitted by the phosphormixture when made up and about 250 microwatts at the end of three years,with the luminous light output decreasing from .24 to .11 lumens in thethree year period. This light output is converted by the cells to about27 inicrowatts at the beginning and about 13 microwatts at the end ofthe period. These cells are capable of providing a voltage of about .25per cell at the end of three year For example, silicon and cadmiumsulphide type cells are suitable for this purpose.

' Preferably, 'where two or more cells -13 are utilized, these cells areconnected in a series circuit, as shown in FIG. 3, whereby the sum e ofthe cell voltages is of a value to operate an electromagnetic device(not shown).

The photocell-source assembly described herein may further be encased intantalum .or its equivalent having a thickness of about .077 inch,whereby the completed unit does not constitute a health hazard.

As previously indicated herein the source could be in a liquid phosphor,forexample, Pm Cl in a solution of para-terphenyl in dioxane.

From the foregoing description, it will be seen that the presentinvention provides an energy source device or battery which is simpleand practical and sufiiciently efiicient to produce electrical energyfor a useful purpose. The specific ilustrative embodiment herein has theadvantageous characteristics of negligible radiation damage to thecontainer and the photocells, the source and phosphor arrangementresults in almost all of the radioactive emissions being absorbed in thephosphor, and light is radiated and/or reflected from the phosphor tothe photocells in an eflicient manner.

The energy which is not converted to electricity appears as heat, butthe calorific value thereof is so low that no sensible heating can occurwhich might cause thermal disintegration of the device.

As various changes may be made in the form, construction and arrangementof the parts herein, without departing from the spiritand scope of theinvention and without sacrificing any of its advantages, it is to beunderstood that all matter hereinis to be interpreted as i1- lustrativeand not in any limiting sense.

I claim:

1. A unitary source device for converting the disintegration energy of aradioactive source to electricity comprising a sealed receptacle havingclosely spaced opposite walls joined by a side wall defining a spacetherein, at least one of said opposite walls having a portion capable oftransmitting light outwardly from said space, a phosphor and aradioactive beta particle source free of nonlight generating beta rayenergy absorbent material confined and arranged in said spacesubstantially to fill the same so that light emitted by said phosphor inresponse to disintegration of said source is directed outwardly throughsaid one opposite wall with absorption of beta particles from saidsource by said phosphor,

and a photovoltaic cell overlying said light transmitting wall portionand having photosensitive means disposed to respond to light transmittedthrough said wall portion from inside the receptacle.

2. A device according to claim 1, wherein said source and said phosphorare present in the form of powder.

3. A device according to claim 1, wherein at least portions of saidsource and said phosphor are present in intimate admixture.

4. A device according to claim 1, wherein said source is admixed in aliquid phosphor.

5. A device according to claim 1, wherein said receptacle has lightreflective means on a wall thereof facing the interior of saidreceptacle.

6. A device according to claim 1, wherein said light reflecting meanshas beta ray shielding properties.

7. A unitary energy source device for converting the disintegrationenergy of a radioactive source to electricity comprising a sealedreceptacle having a space therein and a wall formed with a plurality ofportions through which light can be transmitted outwardly from saidspace, a radioactive source of beta particles and a phosphor confinedand arranged in said space to substantially fill the same so that lightemitted by said phosphor in response to disintegration of said source isdirected outwardly through said portions, said source and said phosphorbeing present in an amount to produce sulficient light for causingphotovoltaic cell means to produce an electrical output on an order toperform useful work, and a photovoltaic cell overlying and closing eachof said light transmitting portions and having means presenting a lightsensitive material at said portions to thereby be energized by saidtransmitted light, said cells being connected in circuit for utilizingthe combined output thereof.

8. A unitary energy source device for converting the disintegrationenergy of a radioactive source to electricity comprising a sealedreceptacle having a space therein and a wall formed with a portionthrough which light can be transmitted outwardly from said space andprovided at other portions with light reflecting means facing theinterior of said receptacle, a radioactive source of beta particles anda phosphor combined and arranged in said space to substantially fill thesame, so that light emitted by said phosphor in response todisintegration of said source is directed outwardly through saidportion, said source and said phosphor being present in an amount toproduce suflicient light for causing photovoltaic cell means to producean electrical output on an order to perform useful work, and aphotovoltaic cell secured to said receptacle and having means presentinga light sensitive material overlying said portion to thereby beenergized by said transmitted light.

9. A unitary energy source for converting the disintegrationenergy of aradioactive source to light comprising a disc-like sealed receptaclehaving closely spaced opposite walls joined by a side wall defining aspace therein, said opposite walls having light transmitting windowsformed therein, a radioactive beta particle source layer free ofnonlight generating beta ray energy absorbent material in saidreceptacle, layers of light generating beta particle responsive phosphordisposed between said radioactive source layer and each of said oppositewalls, respectively, said layers substantially filling said space andsaid phosphor layers being substantially impervious to beta particlesemitted by said source layer.

10. A device according to claim 9, wherein said intermediate layercomprises an admixture of beta particle source material and a phosphor.

11. A device according to claim 10, wherein said intermediate layercontains an activator for said phosphor.

12. A device according to claim 9, wherein said receptacle wall portionsare formed of transparent material and have light reflecting meansthereon facing the interior of said receptacle formed with openings toprovide said Windows.

13. A device according to claim 12, wherein said light reflecting meansare for-med of a material having beta ray shielding properties.

14. A device according to claim 12, wherein said light reflecting meansare formed with a plurality of openings at each side of said receptaclewall portions to provide said windows.

15. A unitary energy source device for converting the disintegrationenergy of a radioactive source to electricity comprising a disc-likesealed receptacle having a space therein and Wall portions formed oftransparent material at opposite sides thereof; light reflecting meanson said wall portions facing the interior of said receptacle and havinga plurality of openings to provide windows through which light can betransmitted outwardly from said space,

a layer of a phosphor in said receptacle adjacent each inner sidethereof having a window formed therein, an intermediate layer of aradioactive source of beta particles sandwiched between said phosphorlayers, said layers being arranged to substantially fill said space, anda photovoltaic cell positioned adjacent each of said Windows, said cellsbeing in electrical connection for utilizing the combined outputthereof.

References Cited in the file of this patent UNITED STATES PATENTS2,582,981 Fua Jan. 22, 1952 2,681,416 Thompson June 15, 1954 2,754,428'Franks et a1. July 10, 1956 2,769,916 Tittle Nov. 6, 1956 2,871,555Foster Feb. 3, 1959 FOREIGN PATENTS 638,106 Great Britain May 31, 19501,076,816 France Apr. 21, 1954 OTHER REFERENCES Thomas: NuclearBatteries Types and Possible Uses, in Nucleonics, vol. 13, No. 1-1,November 1955, pp. 129- 133; pp. 130431 relied upon.

Wallhausen: Uses of Radioisotopes in the Production of Self-LuminousCompounds, in Nations, vol. 15, Aug. 820, 1955, pages 307-309; page 309relied upon,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,031,519 April 24, 1962 Joseph Silverman It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 4, line 29 for the claim reference numeral "1" read 5 Signed andsealed this 11th day of September 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

